72 lines
2.5 KiB
Diff
72 lines
2.5 KiB
Diff
From: Linus Torvalds <torvalds@linux-foundation.org>
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Date: Sat, 14 Aug 2010 18:44:56 +0000 (-0700)
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Subject: mm: fix page table unmap for stack guard page properly
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X-Git-Tag: v2.6.36-rc1~20
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X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=11ac552477e32835cb6970bf0a70c210807f5673
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mm: fix page table unmap for stack guard page properly
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We do in fact need to unmap the page table _before_ doing the whole
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stack guard page logic, because if it is needed (mainly 32-bit x86 with
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PAE and CONFIG_HIGHPTE, but other architectures may use it too) then it
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will do a kmap_atomic/kunmap_atomic.
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And those kmaps will create an atomic region that we cannot do
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allocations in. However, the whole stack expand code will need to do
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anon_vma_prepare() and vma_lock_anon_vma() and they cannot do that in an
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atomic region.
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Now, a better model might actually be to do the anon_vma_prepare() when
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_creating_ a VM_GROWSDOWN segment, and not have to worry about any of
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this at page fault time. But in the meantime, this is the
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straightforward fix for the issue.
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See https://bugzilla.kernel.org/show_bug.cgi?id=16588 for details.
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Reported-by: Wylda <wylda@volny.cz>
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Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
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Reported-by: Mike Pagano <mpagano@gentoo.org>
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Reported-by: François Valenduc <francois.valenduc@tvcablenet.be>
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Tested-by: Ed Tomlinson <edt@aei.ca>
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Cc: Pekka Enberg <penberg@kernel.org>
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Cc: Greg KH <gregkh@suse.de>
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Cc: stable@kernel.org
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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diff --git a/mm/memory.c b/mm/memory.c
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index 9b3b73f..b6e5fd2 100644
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--- a/mm/memory.c
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+++ b/mm/memory.c
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@@ -2792,24 +2792,23 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
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spinlock_t *ptl;
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pte_t entry;
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- if (check_stack_guard_page(vma, address) < 0) {
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- pte_unmap(page_table);
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+ pte_unmap(page_table);
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+
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+ /* Check if we need to add a guard page to the stack */
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+ if (check_stack_guard_page(vma, address) < 0)
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return VM_FAULT_SIGBUS;
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- }
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+ /* Use the zero-page for reads */
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if (!(flags & FAULT_FLAG_WRITE)) {
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entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
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vma->vm_page_prot));
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- ptl = pte_lockptr(mm, pmd);
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- spin_lock(ptl);
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+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
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if (!pte_none(*page_table))
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goto unlock;
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goto setpte;
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}
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/* Allocate our own private page. */
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- pte_unmap(page_table);
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-
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if (unlikely(anon_vma_prepare(vma)))
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goto oom;
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page = alloc_zeroed_user_highpage_movable(vma, address);
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